The present invention relates generally to control valves, particularly for fluid flow control in a hydraulic fluid flow system, and relates more specifically to apparatus for electrically controlling the operational positioning of such control valves.
Various forms of electrically-operated valve apparatus are known wherein an electric motor is operatively connected to a valve for selective movement of the valve between open and closed positions upon manual operation of a control switch or switches, with limit or other positioning switches being provided to automatically stop the operation of the motor when the valve attains the desired open or closed position, example of such apparatus being disclosed and described in U.S. Pat. Nos. 3,520,332; 3,680,831; and 3,862,739. Such valve apparatus typically requires initial manual actuation of each valve movement, whereby operative movement of the valve to one open position requires manual actuation of an appropriate manually-operable switch, such movement being stopped by an associated limit switch, and return movement of the valve to its closed position requires a separate subsequent manual actuation of a manually-operable switch with another associated limit switch stopping such return movement of the valve. Such valve apparatus have the disadvantage that the distraction, forgetfulness, preoccupation or similar negligence of the operator may cause him to leave the valve apparatus running unattended past the point at which it is desired to stop the valve's operation. Such occurences create the danger that the unattended apparatus may potentially cause injury to the operator or other workers and may damage the apparatus or the workpiece on which it is operating.
Other valve apparatus are known wherein one or more electrically-actuated solenoids are employed to control movement of the valve to its operative disposition or disposition upon actuation of the appropriate solenoid and to cause the valve to automatically return to its original starting disposition upon deactuation of the solenoid. However, while such solenoid-operated valve apparatus overcome the aforementioned disadvantages of limit switch controlled valve apparatus, the solenoid-operated valve apparatus are generally more expensive than comparable limit switch controlled apparatus because of the more expensive solenoid components and furthermore are less reliable in that they require more frequent repairs and have a generally shorter lifespan making tham unsuitable for heavy duty applications requiring repetitive solenoid operation.
In contrast, the present invention provides electrically-operated control valve apparatus wherein only the initial actuation of movement of the valve from its closed position to an open operative position must be performed manually, the movement of the valve being automatically deactuated at the operative position and the return movement of the valve to its closed position being automatically effected upon cessation of the manual valve actuation.